生命科学实验中心
专业视频视频列表
转座机制
DNA突变机制
Building Libraries Clone libraries offer the advantage of real libraries: orderly access to information. In most clone libraries, fragments of human DNA are stored in a kind of bacterium, E. col
Subclones To sequence the human genome, Human Genome Project scientists cut relatively large clones called BACs, which are 100,000 to 200,000 bases long , into smaller fragments. The smaller fra
E. Coli Storage E. coli cells containing fragments of human DNA can be stored in freezers indefinitely. When researchers are ready to retrieve DNA from the library, they revive the cells by brin
Preparing DNA for Sequencing The next morning, the cells are broken up to release the DNA inside. The DNA is separated from the cell debris and washed clean. Now there are enough clea
Sequencing Reactions A sequencing reaction includes four main ingredients. Template DNA copied by the bacteria; free bases, the building blocks of DNA that come in 4 types; short pieces of DNA –
Products of Sequencing Reactions A completed sequencing reaction contains an array of colored DNA fragments. The shortest are the length of the primer plus one colored base. The longest fr
Separating the Sequencing Reactions The DNA molecules produced in the sequencing reaction are separated by a process called electrophoresis. DNA molecules are negatively charged. The sequencing
Reading the Sequencing Products In the sequencing machine, a laser excites the fluorescent dyes, and a camera detects the lights that the excited dyes emit. One by one, the sequencing mach
Assembling the Results A computer program helps integrate the information from individual sequencing reactions. It spots where fragments overlap, to puzzle the pieces back together. Many overlap
Working Draft Sequence The Human Genome Project scientists have agreed that whenever they assemble a stretch of DNA that spans 2000 or more letters, they will send the data within 24 hours to pu
Conclusion Some gaps and ambiguities will remain in the representative genome sequence until each letter of DNA has been sequenced approximately 9 times. The working draft has just half of that
Before shredding the DNA in the genome and starting to sequence, Human Genome Project researchers first built a map of the genome. They found thousands of landmarks scattered throughout the chro
Intro Studying the human genome – the complete set of human genes – is a way of studying fundamental details about ourselves. A four-letter alphabet makes up the 3-billion-letter-long sequence o
